Do you guise think imageboards have a future? No doubt things like 4chan will continue to exist, but for smaller websites will less funding and manpower moderation would only get harder.
Would an invite-only imageboard work? Invite-only forums have existed in the past, but one of the redeeming qualities of imageboards are no reputations and less namefag drama. Hypothetically speaking you'd only need a user+pass for an account to access it, but posting is still anonymous.
Invites could be links with expire or account approval, and the selling point would be less need for moderation and a community of like minded individuals. Might even replace discord possibly.